1. Field of the Invention
The present invention relates to a magnetic disk system, and more particularly to a magnetic disk system in which a spindle motor supports a plurality of magnetic disk mediums.
2. Description of the Related Art
A magnetic disk system represented by a hard disk is widely used as an internal or external auxiliary mass-storage device of a personal computer (PC) or the like. With an increasing capacity, a plurality of magnetic disk mediums is generally used in a magnetic disk system. The magnetic disk mediums are rotated in a state of being fixed to a spindle which is driven by a motor, and the data is read and written therefrom and therein while magnetic heads positioned on the both sides of each magnetic disk medium in a floating state move in a radius direction by the drive of access arms.
The magnetic disk medium is formed by uniformly applying the magnetic material to a metallic disk and formatted according to the predetermined standard. A lot of magnetic bands referred to as a track are formed concentrically on the magnetic disk medium and each track is divided into section referred to as a sector, in a circumferential direction. A group of several sectors is referred to as a cluster. A plurality of magnetic heads respectively provided to the magnetic disk mediums is moved integrally and each magnetic head is arranged to be positioned on the same track (on the concentric circles) of each magnetic disk medium. A group of tracks positioned at the same distance from the center of a plurality of magnetic disk mediums is referred to as a cylinder.
FIG. 5 shows the principle of access in the conventional magnetic disk system. For convenience""s sake, a magnetic disk system having two magnetic disk mediums 71 and 72 will be described here. In the conventional magnetic disk system, continuity of sectors is defined by the cylinder, in order to assure efficiency of access.
More specifically, assuming that access starts from the sector address xe2x80x9c1xe2x80x9d of the magnetic disk medium 71, the adjacent sector address xe2x80x9c2xe2x80x9d of the same track is next accessed, and thereafter the sectors from the address xe2x80x9c3xe2x80x9d to the last address xe2x80x9c100xe2x80x9d of the same track are sequentially accessed. Access to the sector address xe2x80x9c101xe2x80x9d is obtained from a given sector of the magnetic disk medium 72 positioned in the same cylinder, not from the magnetic disk medium 71. That is, the access to the sector address xe2x80x9c101xe2x80x9d is obtained by another magnetic head. After the access to the sector address xe2x80x9c101xe2x80x9d, the sector address xe2x80x9c102xe2x80x9d adjacent to the sector address xe2x80x9c101xe2x80x9d on the same track is accessed, thereinafter each adjacent sector address is accessed one after another until the last sector address xe2x80x9c200xe2x80x9d on the same cycle is accessed.
The above-mentioned conventional magnetic disk system, however, has a problem in that when lessening the space between a magnetic head and a magnetic disk medium for improving surface density, micro dusts lying in this space will damage the stable floating characteristic of a magnetic head and easily cause a head crash. The surface density is closely related to the space between a magnetic head and a magnetic disk medium; specifically, as the space becomes narrower, the surface density is further improved, while the system is more easily influenced by the micro dusts. Thus, in order to reduce the probability of producing a head crash, there exists a system having an additional function (referred to as xe2x80x9cpatrol seekxe2x80x9d) of moving a head at regular intervals of, time so that the micro dusts should not accumulate.
As computer systems develop, the storing capacity of a magnetic disk system is increased. Concretely, the surface density has increased at an annual rate of 60% or so. As a result, makers of a magnetic disk system are changing the model of a magnetic disk system every year to ship the magnetic disk system whose capacity is doubled.
Therefore, a magnetic disk system of a small capacity will disappear from the market in a year or so, becoming obsolete in a short time. The above-mentioned patrol seek cannot move a magnetic head without the range that has been adjusted to the disk capacity at system construction; accordingly, when a magnetic disk system of a large capacity is newly mounted on an old-fashioned system, it is impossible to perform the patrol seek on the portion beyond the capacity of the old system.
Further, since the continuity of the sectors is assured by the track on a recording surface, the range to be patrolled on the recording surface is restricted. In other words, access is not uniformly made on the whole recording surface but concentrates on a given area. Therefore, at the power-on and off, when a magnetic head having been saved at the inner circumferential portion returns to the access area again, there increases the probability of passing over micro dusts, which results in increasing the probability of causing a head crash.
An object of the present invention is to provide a magnetic disk system capable of reducing head crash caused by micro dusts by enabling the patrol seek over the whole disk medium.
According to one aspect of the invention, a magnetic disk system comprises
means for supporting and rotating a plurality of magnetic disk mediums formatted by a plurality of tracks and sectors into which the tracks are divided in a circumferential direction,
magnetic heads respectively positioned on each recording surface of the plurality of magnetic disk mediums, for reading and writing data from and to the magnetic disk mediums,
means for instructing the magnetic heads to perform a seek operation, and
control means for controlling data reading and writing from and to the magnetic disk mediums during the seek operation,
the control means including
format selecting means for selecting either a first format continuing the order of the sectors from a track on a magnetic disk medium to a track on another magnetic disk medium in the same cylinder, or a second format continuing the order of the sectors from a track on a magnetic disk medium to another track on the same recording surface, then to format the magnetic disk medium.
In the preferred construction, the format selecting means formats the magnetic disk mediums in such a way that the order of the sectors is continuous from the outermost circumferential track to the inner track of the magnetic disk medium, in the second format.
In another preferred construction, the format selecting means formats the magnetic disk mediums in such a way that the order of the sectors is continuous from the most inner track to the outer track of the magnetic disk medium, in the second format.
According to another aspect of the invention, a magnetic disk system comprises
means for supporting and rotating a plurality of magnetic disk mediums having recording surfaces formatted with a plurality of tracks, each track divided into sectors in a circumferential direction,
magnetic heads respectively positioned on each recording surface of the plurality of magnetic disk mediums, for reading and writing data from and to the magnetic disk mediums,
means for instructing the magnetic heads to perform a seek operation, and
control means for controlling data reading and writing from and to the magnetic disk mediums while the seek operation is performed,
the control means including
determining means for determining an access state of the magnetic disk mediums by the magnetic heads, and
access selecting means for selecting either a first mode of accessing the sectors from a track on a magnetic disk medium to a track on another magnetic disk medium in the same cylinder or a second mode of accessing the sectors from a track on a magnetic disk medium to another track on the same magnetic disk medium based on the access state, and then accessing the magnetic disk mediums according to the selected mode.
In the preferred construction, the access selecting means accesses the magnetic disk mediums in such a way that the order of the sectors is continuous from the outermost circumferential track to the inner track of the magnetic disk medium in the second mode.
In another preferred construction, the access selecting means accesses the magnetic disk mediums in such a way that the order of the sectors is continuous from the most inner track to the outer track of the magnetic disk medium in the second mode.
In another preferred construction, the access selecting means checks whether access is concentrated in only one area of a track of the magnetic disk medium more than a predetermined period during the access state; when access is not concentrated more than a predetermined period, the means selects the first mode, while when access is concentrated, the means selects the second mode.
In another preferred construction, the access selecting means checks whether access is concentrated in only one area of a track on the magnetic disk medium more than a predetermined period during the access state; when access is not concentrated more than a predetermined period, the means selects the first mode, while when access is concentrated, the means selects the second mode, and after selecting the second mode, the means switches the second mode to the first mode when a predetermined period has elapsed.
Other objects, features and advantages of the present invention will become clear from the detailed description given herebelow.